Semiconductor devices capable of providing blocking voltages of the order of 10.sup.3 volts or higher are well known in the art. Typical devices are diodes and thyristors. Generally, these devices are also intended to carry substantial currents, e.g., 1-100 amperes.
It is known that in order to provide blocking voltages of 10.sup.3 volts or higher, great care must be taken to control the electric field distribution where the blocking junction intersects the device surface. If this is not done properly, then flash-over or channeling or both will occur and device operation will be unsatisfactory.
Because of their widespread use, there is a continuing need to find improved structures and manufacturing methods for high voltage semiconductor devices so that performance may be improved and/or cost reduced or a combination thereof. Accordingly, it is an object of the present invention to provide an improved means and method for semiconductor devices, particularly semiconductor devices employing high voltage blocking junctions, wherein the number of manufacturing steps is maintained or reduced while manufacturing yield is improved for the same or better device performance than with the prior art. While the present invention is advantageous for use with any type of high voltage blocking junction, it is particularly useful for very high voltage, high current diodes, thyristors, transistors and the like, and it is therefore a further object to provide an improved means and method for such devices.
There are two general categories of devices known in the art; mesa devices where the blocking junction intersects a die or groove sidewall, and planar devices where the blocking junction intersects a major face of the die. Each has advantages and disadvantages. The present invention is most useful with mesa structures but may also be applied in combination with planar structures.